Control device for camshaft systems

ABSTRACT

A control device for camshaft systems of an internal combustion engine with n banks of cylinders arranged in a V-shaped configuration. The control device has a distribution system with a first distributor gear which intermeshes with an output gear arranged on a crankshaft of the internal combustion engine. The distribution system has m&lt;n secondary distributor gears which intermesh with the first distributor gear and transmit a driving force to the n camshaft systems of the n banks of cylinders through n endless-chain drives.

BACKGROUND OF THE INVENTION

The invention relates to a control device for camshaft systems of aninternal combustion engine with n banks of cylinders arranged in aV-shaped configuration, the control device having a distribution systemwith a first distributor gear, which intermeshes with an output geararranged on a crankshaft of the internal combustion engine.

A central output of generic type for an internal combustion engine of amotorcycle is disclosed by U.S. Pat. No. 4,671,223. In this case astraightforward gear drive is produced, a separate distribution systembeing assigned to each camshaft system of one bank of cylinders. Thegears of each distribution system are mounted in a respective frame. Thestraightforward gear drive has the disadvantage that it generates veryloud noise. Furthermore, having a separate output line for each camshaftsystem makes this arrangement mechanically expensive, and it takes up alot of space. A central output for the control device of an internalcombustion engine for a motor vehicle would not be practically feasiblewith this system, since all cylinder banks would have to have at leastone division. This would lead, however, to considerable mechanicalweakening of the engine block, which with the torques and forcesoccurring in motor vehicles could not be tolerated.

A central control output is furthermore disclosed in the article “ThePorsche 4.5-liter Racing Sports Car, Type 917” by H. Metzger, whichappeared in the offprint from a German periodical, AutomobiltechnischeZeitschrift (ATZ), Vol. 71 No. 9/12/1969, pages 313 to 320 for anair-cooled four-stroke engine with two flat rows of cylinders, which isdesigned especially for racing purposes. The drive to four camshaftscomes from a central output gear on the crankshaft to both rows ofcylinders, in each case by way of five straight-toothed gears onneedle-roller bearings. In other words, a separate control device isassigned to each row of cylinders. The five gears arranged betweencrankshaft and each of the camshafts are in each case arranged in a gearhousing, which can be bolted to a crankcase. This, too, is astraightforward gear drive, which has the aforementioned disadvantagethat it generates considerable noise levels. In the case of a racing carfor a Constructors' World Championship this may not be critical, but fora comfortable motor vehicle for day-to-day use in public road traffic itis unacceptable.

SUMMARY OF THE INVENTION

The object of the present invention therefore is to provide a simplecontrol device of the above-mentioned type that takes up little overallspace and overcomes the above-mentioned disadvantages.

To this end it is proposed, according to the invention, that thedistribution system have m<n secondary distributor gears, whichintermesh with the first distributor gear and transmit a driving forceto the n camshaft systems of the n banks of cylinders through nendless-chain drives.

This has the advantage that all camshaft systems of respective cylinderscan be driven by a single distribution system proceeding from the middleof the internal combustion engine, for example. This advantageouslysimplifies the mechanical construction of the control device and reducesthe overall space required and the weight.

A particularly space-saving central output for the control device isobtained by arranging the output gear centrally on the crankshaft.

It is advisable if m=n−1 or m=n−2, it being particularly preferable ifn=2, 3 or 4.

For ease of assembly the first and the secondary distributor gears arearranged in a common carrier, which when pre-assembled can be fixed to acrankcase of the internal combustion engine. For example, with a centraloutput for the control device, bolting the carrier onto the crankcaseprovides additional reinforcement for the engine block, which isactually mechanically weakened by corresponding recesses required forthe central output.

Simple assembly of the control device, for example in a recess in acrankcase for a central output, is achieved by providing a module thatcarries the endless-chain drive between each secondary distributor gearand each camshaft system. The module being pre-assembled so that itcarries a chain sprocket, which can be frictionally and coaxially fittedto the respective secondary distributor gear, at one end and at leastone camshaft gear on an opposite end, the endless-chain drive passingaround the chain sprocket and the camshaft gear.

A suitable transmission ratio between the crankshaft and the respectivecamshaft system is effectively achieved by selecting a tooth ratio ofthe secondary distributor gear to the chain sprocket such that acrankshaft to camshaft system transmission ratio of 2:1 is obtained.

Secure guiding of the chain of the endless-chain drive is achieved inthat the module has a U-shaped guide plate for the endless-chain driveon the idle strand side.

Reliable, frictional running of the chain of the endless-chain drivewith low mechanical wear and low noise is achieved in that the modulehas a chain-tensioning fixture on the load strand side.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, advantages and advantageous developments of theinvention follow from the following description of an example of anembodiment of the invention, with reference to the drawings attached, inwhich

FIG. 1 shows a front view of a preferred embodiment of a control deviceaccording to the invention,

FIG. 2 shows a perspective view thereof,

FIG. 3 shows a front view of a carrier for a distribution system of acontrol device according to the invention,

FIG. 4 shows a top view thereof,

FIG. 5 shows a sectional view along the line A—A in FIG. 3,

FIG. 6 shows a sectional view along the line B—B in FIG. 3 and

FIG. 7 shows a side view of a module of a control device according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The preferred embodiment of a control device according to the inventionrepresented in FIGS. 1 and 2 comprises an output gear 12 arranged on acrankshaft 10, which gear intermeshes with a first distributor gear 14.Two secondary distributor gears 16 and 18, which are coaxially arrangedand frictionally connected with chain sprockets 20, 22 and 24 of eachmodule 26, 28 and 30 respectively, intermesh with a distributor gear 42,frictionally coupled to the first distributor gear 14, only theintermediate gears 20 and 24 being visible in FIGS. 1 and 2. The chainsprocket 22 is hidden behind the chain sprocket 20 (cf. FIG. 5).

Power is transmitted by way of respective endless-chain drives 32 toeach of the camshaft gears 34, which are frictionally connected tocorresponding camshafts (not shown). In so doing, the modules 26, 28 and30 carry the respective chain sprockets 20, 22, 24 at one end and thecamshaft gears 34 at an opposite end, the respective endless-chain drive32 passing around the chain sprockets 20, 22 and 24 and the associatedcamshaft gears 34. The endless-chain drive 32 results in an essentiallyvibration-neutralized or vibration-damped power transmission.

In the embodiment represented in FIG. 1, the output gear 12 of thecrankshaft 10 also intermeshes with a further distributor gear 36, whichby way of a frictionally coupled gear 33 intermeshes with a firstintermediate gear 35, which in turn intermeshes with a secondaryintermediate gear 38. The secondary intermediate gear 38 in turnintermeshes with a drive gear 40 of an oil pump (not shown), so that thecrankshaft 10, by way of its output gear 12, simultaneously drives theoil pump. The distributor gear 35 has, for example, thirty-seven teeth,the first intermediate gear 36 eighteen teeth, the secondaryintermediate gear 38 eighteen teeth and the drive gear 40 eighteenteeth.

For the control device, a transmission ratio from the crankshaft 10 tothe camshaft gears of 2:1 is needed. This is achieved, for example, bythirty-eight teeth on the output gear 12, sixty-four teeth on a smallergear rim 42 of the intermediate gear 14, fifty-seven teeth on thesecondary distributor gears 16, 18, eighteen teeth on the chainsprockets 20, 22, 24 and thirty-two teeth on the camshaft gears 34.

The embodiment of a control device according to the inventionrepresented in FIGS. 1 and 2 is designed for an internal combustionengine with three rows of cylinders arranged in a V-shaped configurationand denoted below by the letters A, B and C, each module 26, 28 and 30being assigned to a row of cylinders A, B or C or to a respectivecamshaft system of a row of cylinders A, B or C. It will be immediatelyapparent that all three camshaft systems of the three rows of cylindersare actuated by just one distribution system 14, 16, 18.

The arrangement represented by way of example is thereby particularlysuitable for a central output for the control device, since in order tobring the control device out away from the crankshaft 10, that is froman inner area of a crankcase (not shown), to the external camshaft gears34, only one of the rows of cylinders, namely the middle cylinder row B,needs to have a central recess or division. The adjacent rows ofcylinders A and C may be designed without a division as continuouscylinder rows A and C. The camshaft gears 34 of the two adjacent rows ofcylinders A and C are actuated by the modules 26 and 30 likewiseproceeding from the middle row of cylinders B.

The first and the secondary distributor gears 14, 16 and 18 are arrangedin a common carrier 44, as can be seen from FIGS. 3 and 4. Said carrier44 holds the first distributor gear 14 and the secondary distributorgears 16 and 18, it being possible, for example, to insert thepre-assembled carrier into a recess or division in the middle bank ofcylinders B and to bolt it to the crankcase. Respective insertion guides46, 48 and 50 for each of the modules 26, 28 and 30 are furthermoreformed on the carrier 44. After fixing the carrier 44 on the crankcase,the modules 26, 28 and 30 each with pre-assembled chain sprockets 20, 22and 24 together with pre-assembled camshaft gears 34 and endless-chaindrive 32 can be inserted into said insertion guides 46, 48 and 50. Assoon as all gears are at their predetermined location, they can berotatably fixed to the corresponding shaft and bearings.

This is the case for the chain sprockets 20, 22 together with thesecondary distributor gear 16 in FIG. 5. When fitted on a common shaft52, these gears 16, 20 and 22 are non-positively connected to oneanother by frictional adhesion, a central bolt 54 fixing thisarrangement. The shaft 52 is mounted so that it can rotate by means ofball bearings 56 in relation to the carrier 44. The central boltfurthermore fixes a gear 58, which serves as drive for a water pump (notshown).

FIG. 6 illustrates the arrangement of the secondary distributor gear 18with the chain sprocket 24 in the assembled state. In this case, a shaft60 is provided, which is fixed by two central bolts 62 and 64. Thecentral bolt 64 furthermore fixes a gear 66, which serves for a drivefor a further water pump (not shown). The two aforementioned water pumpsare, for example, arranged directly adjacent to the carrier 44 inrespective V-shaped intermediate spaces between the rows of cylinders Aand B or B and C in such a way that their drive gears intermesh directlywith each of the gears 58 and 66 respectively.

FIG. 7 illustrates, by way of example, the module 26 for cylinder row A.Said module 26 comprises a frame 68 and a U-shaped guide plate 70 on theidle strand side with a running surface 72 for the chain of theendless-chain drive, not shown in FIG. 7. When pre-assembled, the chainpasses around the chain sprocket 20 and the camshaft gears 34 and holdsthese fast to the frame 68, no further fixing of any kind beingotherwise provided for the chain sprocket 20 and the camshaft gears 34.Only after fitting or inserting the modules 26, 28 and 30 are thesefinally rotatably fixed by means of corresponding shafts, such as theaforementioned shafts 52 and 60 for the chain sprockets 20, 22 and 24,for example. A chain tensioning fixture 72, for example, is provided onthe load strand side, as can be seen from FIG. 2.

We claim:
 1. A control device for camshaft systems of an internalcombustion engine with a crankshaft and n banks of cylinders arranged ina V-shaped configuration, the control device comprising: a distributionsystem with a first distributor gear; an output gear arranged on thecrankshaft so as to intermesh with the first distributor gear, thedistributor system having m<n secondary distributor gears whichintermesh with the first distributor gear; and n endless-chain drivesoperatively connected to the secondary distribution gears and thecamshaft systems so as to transmit a driving force to the n camshaftsystems of the n banks of cylinders.
 2. A control device as defined inclaim 1, wherein the drive gear is arranged centrally on the crankshaft.3. A control device as defined in claim 1, wherein m=n−1.
 4. A controldevice as defined in claim 1 wherein m=n−2.
 5. A control device asdefined in claim 1, wherein n=2.
 6. A control device as defined in claim1, wherein n=3.
 7. A control device as defined in claim 1, wherein n=4.8. A control device as defined in claim 5, wherein the first distributorgear and the secondary distributor gears are arranged in a commoncarrier which is fixable to a crankcase of the internal combustionengine.
 9. A control device as defined in claim 1, and furthercomprising a module that carries the endless-chain drive providedbetween each secondary distributor gear and each camshaft system, themodule being preassembled so as to carry a chain sprocket, which isfrictionally and coaxially fittable to the respective secondarydistributor gear, at one end and at least one camshaft gear on anopposite end, the endless-chain drive passing around the chain sprocketand the camshaft gear.
 10. A control device as defined in claim 9,wherein a tooth ratio of the secondary distributor gear to the chainsprocket is such that a crankshaft to camshaft system transmission ratioof 2:1 is obtained.
 11. A control device as defined in claim 9, whereinthe module has a U-shaped guide plate for the endless-drive on an idlestrand side.
 12. A control device as defined in claim 9, wherein themodule has a chain-tensioning fixture on a load strand side.
 13. Acombination comprising: an internal combustion engine having acrankshaft, cam shaft systems and n banks of cylinders arranged in aV-shaped configuration; and a control device for the camshaft systems,the control device including a distribution system with a firstdistributor gear, an output gear arranged on the crankshaft so as tointermesh with the first distributor gear, the distribution systemhaving m<n secondary distributor gears which intermesh with the firstdistributor gear, and n endless-chain drives operatively connected tothe secondary distribution gears and the camshaft system so as totransmit a driving force to the n camshaft systems of the n banks ofcylinders.